Traveling bag is commonly used for carrying personal goods during traveling from place to place. According to their sizes, shapes, storage volumes, and carrying methods, traveling bags can generally be classified into shoulder bags, waist bags, hand bags, and back packs.
Waist bag comprises a bag body and a waist belt having two ends connected to two sides of the bag body respectively for tightening around the user's waist, so that the user's hands are free for other purposes. Shoulder bag comprises a bag body and a longer shoulder belt having two ends connected to two sides of the bag body respectively for carrying on the user's shoulder. Back pack contains a back bag body as large as the user's back, wherein two shoulder belts are connected to a rear side of the back bag body, so that the back pack can be carried by looping two shoulder belts around the user's two shoulders respectively.
It is well known that the back pack generally contains a larger storage volume than either the waist bag or the shoulder bag. Moreover, the back pack also has a bigger carrying power since it is carried by the two strong shoulders of the user, so that the back pack can be used as a school bag to carry the heavy books or a picnic bag to carry more outdoor stuffs and tools. Sometimes, we may only need a smaller bag to carry our personal goods such as wallet, keys, notebooks, and etc. The waist bag or shoulder bag provides a good size for such usage. Therefore, most people have to spend extra expense to purchase all the waist bag, shoulder bag and the back pack for different usage.
However, occasionally, we go outside with a few personal stuffs and returning with a lot of shopping goods. But a waist bag is still a waist bag. None of the conventional waist bag or shoulder bag can selectively provide additional storage volume. Of course, we may go outside with a back pack for carrying the shopping goods but most people won't do that because it looks very stupid to carry only a few things with a relatively large pack.